Various cleaning compositions have been used for cleaning automotive wheels. Detergent formulations have been commercialized for such usage, but they have the disadvantage of requiring much scrubbing and hard work to remove the soils adhered to the wheels. Generally such formulations are only partially effective.
Acid cleaners replaced detergent formulations as the cleaning composition of choice for wheels. These cleaners usually consist of strong acids such as phosphoric, hydrochloric, sulfuric, oxalic, acetic, hydroxyacetic, hydrofluoric, and citric acids, as well as blends of the various acids. These products are not very effective in removing road soils from wheels. They have the additional disadvantage in that they are highly corrosive to wheels, paints and plastics and tend to strip paint and chrome and discolor aluminum and chrome. These products often require neutralization steps with strongly alkaline solutions which can also cause corrosion and pitting.
Another type of wheel cleaner is based on alkaline hard surface cleaners. These formulas consist mainly of detergents, water soluble organic solvents such as glycol ether, and alkaline materials such as sodium hydroxide, potassium hydroxide, and/or any of the alkaline silicates and phosphates. The disadvantages of these products are that they are not very effective at cleaning wheel soils, and the highly alkaline nature can damage painted and aluminum surfaces. Also, if they are allowed to dry on the surface, they tend to leave insoluble residues.
Outside of the automotive care industry, various other types of cleaning formulations have been devised for use an metal surfaces and industrial machinery. However, such compositions generally have to be used at elevated temperatures and typically work by etching the surface that is cleaned. For example, U.S. Pat. No. 4,614,607 describes a gelled deoxidizer comprising an aqueous solution of nitric acid, sulfuric acid, ammonium bifluoride, and fumed silica which cleans aluminum by way of a constant etching rate.
U.S. Pat. No. 3,969,135 discloses the use of ammonium fluoride in cleaning compositions for removing residues on aluminum surfaces which remain after the production of the metal. To be effective, the cleaning composition is used at elevated temperatures, around 120.degree. F.
British patent No. 1,179,860 discloses an aqueous alkaline cleaning solution for use on galvanized metals. The cleaning solution comprises fluoride salts and soluble soaps in an alkaline aqueous solution. Effective cleaning occurs at elevated temperatures between 120.degree.-160.degree. F.
U.S. Pat. No. 4,346,128 describes a tank process for plating aluminum substrates. The process first involves a cleaning step of immersing the substrate in a low pH dilute acid bath containing an acidic fluoride-containing salt so as to remove surface contaminants from the substrate. However, this cleaning process results in some etching of the substrate.